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package sshd
import (
"context"
"errors"
"fmt"
"reflect"
"time"
"gitlab.com/gitlab-org/labkit/log"
"golang.org/x/crypto/ssh"
grpccodes "google.golang.org/grpc/codes"
grpcstatus "google.golang.org/grpc/status"
shellCmd "gitlab.com/gitlab-org/gitlab-shell/v14/cmd/gitlab-shell/command"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/command"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/command/readwriter"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/command/shared/disallowedcommand"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/config"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/console"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/metrics"
"gitlab.com/gitlab-org/gitlab-shell/v14/internal/sshenv"
)
type session struct {
// State set up by the connection
cfg *config.Config
channel ssh.Channel
gitlabKeyId string
gitlabKrb5Principal string
remoteAddr string
// State managed by the session
execCmd string
gitProtocolVersion string
started time.Time
}
type execRequest struct {
Command string
}
type envRequest struct {
Name string
Value string
}
type exitStatusReq struct {
ExitStatus uint32
}
func (s *session) handle(ctx context.Context, requests <-chan *ssh.Request) error {
ctxlog := log.ContextLogger(ctx)
ctxlog.Debug("session: handle: entering request loop")
var err error
for req := range requests {
sessionLog := ctxlog.WithFields(log.Fields{
"bytesize": len(req.Payload),
"type": req.Type,
"want_reply": req.WantReply,
})
sessionLog.Debug("session: handle: request received")
var shouldContinue bool
switch req.Type {
case "env":
shouldContinue, err = s.handleEnv(ctx, req)
case "exec":
// The command has been executed as `ssh user@host command` or `exec` channel has been used
// in the app implementation
shouldContinue, err = s.handleExec(ctx, req)
case "shell":
// The command has been entered into the shell or `shell` channel has been used
// in the app implementation
shouldContinue = false
var status uint32
status, err = s.handleShell(ctx, req)
s.exit(ctx, status)
default:
// Ignore unknown requests but don't terminate the session
shouldContinue = true
if req.WantReply {
if err := req.Reply(false, []byte{}); err != nil {
sessionLog.WithError(err).Debug("session: handle: Failed to reply")
}
}
}
sessionLog.WithField("should_continue", shouldContinue).Debug("session: handle: request processed")
if !shouldContinue {
s.channel.Close()
break
}
}
ctxlog.Debug("session: handle: exiting request loop")
return err
}
func (s *session) handleEnv(ctx context.Context, req *ssh.Request) (bool, error) {
var accepted bool
var envRequest envRequest
if err := ssh.Unmarshal(req.Payload, &envRequest); err != nil {
log.ContextLogger(ctx).WithError(err).Error("session: handleEnv: failed to unmarshal request")
return false, err
}
switch envRequest.Name {
case sshenv.GitProtocolEnv:
s.gitProtocolVersion = envRequest.Value
accepted = true
default:
// Client requested a forbidden envvar, nothing to do
}
if req.WantReply {
if err := req.Reply(accepted, []byte{}); err != nil {
log.ContextLogger(ctx).WithError(err).Debug("session: handleEnv: Failed to reply")
}
}
log.WithContextFields(
ctx, log.Fields{"accepted": accepted, "env_request": envRequest},
).Debug("session: handleEnv: processed")
return true, nil
}
func (s *session) handleExec(ctx context.Context, req *ssh.Request) (bool, error) {
var execRequest execRequest
if err := ssh.Unmarshal(req.Payload, &execRequest); err != nil {
return false, err
}
s.execCmd = execRequest.Command
status, err := s.handleShell(ctx, req)
s.exit(ctx, status)
return false, err
}
func (s *session) handleShell(ctx context.Context, req *ssh.Request) (uint32, error) {
ctxlog := log.ContextLogger(ctx)
if req.WantReply {
if err := req.Reply(true, []byte{}); err != nil {
ctxlog.WithError(err).Debug("session: handleShell: Failed to reply")
}
}
env := sshenv.Env{
IsSSHConnection: true,
OriginalCommand: s.execCmd,
GitProtocolVersion: s.gitProtocolVersion,
RemoteAddr: s.remoteAddr,
}
rw := &readwriter.ReadWriter{
Out: s.channel,
In: s.channel,
ErrOut: s.channel.Stderr(),
}
var cmd command.Command
var err error
if s.gitlabKrb5Principal != "" {
cmd, err = shellCmd.NewWithKrb5Principal(s.gitlabKrb5Principal, env, s.cfg, rw)
} else {
cmd, err = shellCmd.NewWithKey(s.gitlabKeyId, env, s.cfg, rw)
}
if err != nil {
if errors.Is(err, disallowedcommand.Error) {
s.toStderr(ctx, "ERROR: Unknown command: %v\n", s.execCmd)
} else {
s.toStderr(ctx, "ERROR: Failed to parse command: %v\n", err.Error())
}
return 128, err
}
cmdName := reflect.TypeOf(cmd).String()
establishSessionDuration := time.Since(s.started).Seconds()
ctxlog.WithFields(log.Fields{
"env": env, "command": cmdName, "established_session_duration_s": establishSessionDuration,
}).Info("session: handleShell: executing command")
metrics.SshdSessionEstablishedDuration.Observe(establishSessionDuration)
if err := cmd.Execute(ctx); err != nil {
grpcStatus := grpcstatus.Convert(err)
if grpcStatus.Code() != grpccodes.Internal {
s.toStderr(ctx, "ERROR: %v\n", grpcStatus.Message())
}
return 1, err
}
ctxlog.Info("session: handleShell: command executed successfully")
return 0, nil
}
func (s *session) toStderr(ctx context.Context, format string, args ...interface{}) {
out := fmt.Sprintf(format, args...)
log.WithContextFields(ctx, log.Fields{"stderr": out}).Debug("session: toStderr: output")
console.DisplayWarningMessage(out, s.channel.Stderr())
}
func (s *session) exit(ctx context.Context, status uint32) {
log.WithContextFields(ctx, log.Fields{"exit_status": status}).Info("session: exit: exiting")
req := exitStatusReq{ExitStatus: status}
s.channel.CloseWrite()
s.channel.SendRequest("exit-status", false, ssh.Marshal(req))
}
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